1. Technical Field
The present invention relates to Voltage-Controlled Oscillators (VCOs), and more specifically, to VCOs that have wide operating frequency ranges.
2. Related Art
A conventional Voltage-Controlled Oscillators (VCO) comprises multiple delay cells electrically coupled in series and in a loop. More specifically, the outputs of the first delay cell of the VCO are electrically coupled to the inputs of the second delay cell. The outputs of the second delay cell are electrically coupled to the inputs of the third delay cell, and so on. Finally, the outputs of the last delay cell are electrically coupled to the inputs of the first delay cell so as to form the loop. The outputs of any one delay cell of the conventional VCO can be used as the outputs of the VCO.
Each VCO has a specific operating frequency range. This means that the VCO can generate a stable signal with a frequency inside its operating frequency range. In other words, the VCO is not capable of generating a stable signal with a frequency outside its operating frequency range. As a result, it is always desirable to design VCOs having wider operating frequency ranges.
Therefore, a design of a novel VCO that has an operating frequency range relatively wider than that of conventional VOCs is needed. A method is also needed for operating the novel VCO.